As a general rule, devices of this type comprise:
a support plate; PA1 an annulus in contact with the support plate; PA1 a cam housed to rotate in the annulus about a central axis and designed to be mounted to rotate with an outlet member, the cam and the annulus defining at least one running path of varying section; PA1 control member mounted to rotate relative to the support plate about the central axis; PA1 locking means mounted to move in the running path, said locking means being normally in a locked state in which they co-operate with the annulus and the cam to prevent any relative rotary movement of said cam relative to the support plate in the absence of the control member being actuated, said control member being adapted to act on the locking means by placing them in an unlocking state in which they allow the cam to rotate relative to the support plate; and PA1 a closure ring partially defining a housing which encloses the cam and the locking means, said closure ring being fixed to the support plate. PA1 the tabs of the closure ring have free ends and the support plate has holes in register with the free ends, said free ends passing through the holes and being folded back so as to fix the closure ring to the support plate; PA1 the closure ring includes at least two tabs and the annulus has at least two external studs co-operating with said tabs to prevent the annulus from rotating relative to the support plate; PA1 the locking means comprise at least one pair of wheels housed in said running path, said running path having two ends of wedge shape co-operating with respective ones of the wheels to lock the cam in the absence of action on the control member; PA1 the wheels of the pair of wheels are held apart by a resilient member; PA1 the control member comprises a cheek plate mounted to rotate with lost motion relative to the cam and which is provided with at least one pair of fingers projecting into the running path, said two fingers being adapted to push against respective ones of the wheels in the running path to compress the resilient member when the control member is actuated, thereby enabling the cam to rotate relative to the support plate; PA1 the control member has two fingers projecting into the running path, on either side of the pair of wheels, one of the fingers pushing against one of the wheels and releasing the cam to rotate relative to the support plate, and the other finger rotating the cam relative to the support plate when the control member is actuated; and PA1 the closure ring is made of cutout and stamped sheet metal.
Such devices are used in particular for varying the position adjustment of a motor vehicle seat comprising a seat proper which is mounted on a lift device and/or which rotatably supports a seat back. The support plate is generally fixed to the seat back and the control member is driven in rotation by a control knob actuated by a user of the seat.
In the most common applications of locking devices of the above type, the cam is connected either to the seat back or to a lift mechanism.
By means of such devices, the user can vary the height of the seat or the inclination of the seat back while being assured that the seat and the seat back will remain in the desired position after adjustment.
Known locking mechanisms of the above-mentioned type are manufactured in two stages, insofar as it is necessary firstly to make the housing containing the device and then to connect the housing to the support plate. That type of assembly is expensive and increases overall size.